Registering capacity on a cluster or on a single server are two different things.
but here is your answer:
Unified CM Capacity Planning with UCS Platforms
In a virtualized deployment, most Unified Communications applications such as Unified CM must be installed using a predefined template that specifies the configuration of the virtual machine's virtual hardware. These templates are distributed through Open Virtualization Archives (OVA), an open standards-based method for packaging and distributing virtual machine templates.
These OVA templates define the number of virtual CPU, the amount of virtual memory, the number and size of hard drives, and so forth, and they determine the capacity of the application. For Unified CM, there are multiple OVA templates available, one for almost each server class (although there is no template corresponding to the MCS 7815 or MCS 7816). A Unified CM virtual machine instance running on a VMware or Cisco UCS server has the same capacity as a Unified CM node running directly on a Cisco MCS server when using the corresponding OVA template. For example, the OVA template for Unified CM supporting 7,500 users and/or devices has the same capacity as the MCS 7845-H2/I2 server.
Unified CM Capacity Planning Guidelines and Endpoint Limits
The following capacity guidelines apply to Cisco Unified CM:
•
Within a cluster, a maximum of 8 call processing subscriber nodes can be enabled with the Cisco CallManager Service. Other servers may be used for more dedicated functions such as publisher, TFTP subscribers, and media resources subscribers.
•Each cluster can support configuration and registration for a maximum of:
–40,000 secured or unsecured SCCP or SIP endpoints with Unified CM 8.6(1) and later releases
–30,000 secured or unsecured SCCP or SIP endpoints with Unified CM 8.5 and earlier releases.
•A cluster consisting of server node instances running on VMware can support different capacities depending on the OVA template that is chosen. For most Cisco MCS server classes, there is a corresponding OVA template that provides a Unified CM instance with the same capacities (number of phones, gateways, locations, regions, CTI connections, and so forth) as the MCS server class. Because multiple virtual machine instances can run on the same blade or server, the total capacity on a blade or server can therefore be higher than on an MCS server.
•The maximum recommended trace setting for Unified CM is 2,000 files of 2 MB for both System Diagnostic Interface (SDI) and Signaling Distribution Layer (SDL) traces, for a total of 4,000 files. Each process has a setting for maximum number of files, and each process is allowed 2,000 files for SDL and 2,000 files for SDI. Trace settings for all other components must be configured within the limit of 126 MB (for example, 63 files of 2 MB each). These are suggested upper limits. Unless specific troubleshooting under high call rates requires increasing the maximum file setting, the default settings are sufficient for collecting sufficient traces in most circumstances.
For more information about Unified CM capacity planning considerations, including sizing limits as well as a complete discussion of system sizing, capacity planning, and deployment considerations, see the chapter on Unified Communications Design and Deployment Sizing Considerations.
source: http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/8x/callpros.html#wp1287336
please rate if useful
